Grails loading widgets in Parallel - grails

Question

I have some widgets in my application. I want to load them in a single page. It works always when loaded sequentially,but fails(throws exception-java.lang.IllegalStateException-Cannot ask for request attribute - request is not active anymore!) when loaded in parallel. Am I missing something ? Is there any other way to load these in parallel? Please suggest. Here is my code snippet
class TestController {
def widget1() {
render "Widget 1"
}
def widget2() {
render "Widget 2"
}
}
class ManagerController {
def loadSequential(){
def data = [:]
data['view1'] = g.include(action: 'widget1', controller: 'test')
data['view2'] = g.include(action: 'widget2', controller: 'test')
render data['view1']
render data['view2']
}
def loadParallel(){
def data = [:]
PromiseMap pm = new PromiseMap()
pm['view1'] = { g.include(action: 'widget1', controller: 'test') }
pm['view2'] = { g.include(action: 'widget2', controller: 'test') }
def result = pm.get()
render result['view1']
render result['view2']
}
}

Answer 1

Here's my 2p on this matter.
We've tried really hard to make Grails render pages in parallel but we couldn't make it work. After digging really deep we simply found that Grails is not ready for this kind of stuff. It's build in a way where rendering is always thread-exclusive.
I'd say it's all due to the org.codehaus.groovy.grails.web.pages.GroovyPageOutputStack that is not ready for a concurrent access.
I'll watch this space just in case someone managed to make it work.

Answer 2

Try this:
import static grails.async.Promises.*
...
def loadParallel() {
task {
def data = [:]
PromiseMap pm = new PromiseMap()
pm['view1'] = { g.include(action: 'widget1', controller: 'test') }
pm['view2'] = { g.include(action: 'widget2', controller: 'test') }
def result = pm.get()
render result['view1'] + result['view2']
}
}
In the loadSequential() example you are not loading response sequentially, but concatenating two views into a single response. Parallel rendering should be a client side job. See for example how Lift does it with jQuery.